Pump



y 1953 F. J. M KENZIE 2,639,084

' PUMP Filed Aug. 8, 1951 FIGJ M w MTHnflmW'rlMn.

ATTORNEYS Patented May 19, 1953 UNITED STATES- PATENT OFFICE PUMP Frederick J. MacKenzie, Trenton, N. J.

Application August 8, 1951, Serial No. 240,817

3 Claims. (Cl. 230-92) The present invention relates to improvements in methods and means for exhausting vapors or gases from chambers or the like for the development of subatmospheric pressures or vacuum in such chambers.

Various means have previously been proposed for this purpose, including various types of jet pumps. Steam jets have been used, subject to the disadvantage that by this means pressures lower than about 3 inches of mercury absolute are not readily obtainable, if at all, and further the considerable expense of supplying the steam. It has also been proposed to use jet pumps in which water is the ejecting fluid. In such op erations the water has also served as a cooling medium for efiecting condensation or partial condensation of the vapors. This has required a source of water at a temperature below that to which the vapors to be exhausted will condense.

It is an object of my present invention to provide an improved pump of the jet type whereby pressures of the order of inch or less of mer cury absolute may be developed.

A further object is to provide means whereby such low pressures may be developed through the use of water or other noncompressible fluid at a temperature not necessarily below that at which the vapors to be ejected will condense under existing pressure conditions and to create a reduced pressure below that at which the water, for instance, would normally vaporize at the existing temperature. These and other objects are accomplished by my present invention as will appear from the following description.

For purposes of economy I generally prefer to use water as the ejecting fluid and in the following description I shall refer to the ejecting fluid as water. It will, however, be understood that other noncompressible fluids may be used, oil, for instance.

The invention provides an improved pump of the fluid ejector or jet type especially adapted to use in exhausting condensible vapors, the operation of which involves the application and use of principles not heretofore employed, to my knowledge, in vacuum pumps. The invention is also applicable to the exhausting of non-condensible gases.

In the operation of conventional jet pumps there is normally a substantial amount of flash vaporization of the ejector water unless the water used is at a temperature below that at which water vaporizes at the existing low pressure. In accordance with my present invention, I avoid, or at least materially reduce, the amount of such sarily tend to increase.

flash vaporization by developing in the unconfined water jet, a static or internal pressure sufficient to overcome, in part at least, the vapor pressure of the water. The invention is espe cially useful where the available water is at a temperature at which it would vaporize when exposed to the low pressure. However, it will be understood that water at a lower temperature may be used, when available.

Briefly, in the operation of my improved vacuum pump, an annular, swirling stream of water is forced under pressure through an annular nozzle tapering inwardly toward its exit end and, so constructed and arranged with respect to a closed, low pressure zone or chamber in open communication with the chamber from which the vapors are to be exhausted, as to produce in said low pressure zone an unconfined, swirling, annular stream or jet of the water. This annular stream is directed into an annular, Venturi-shaped throat, spaced from, and coax ially positioned with respect to, the nozzle exit, and leading from the said low pressure zone into an enclosed high pressure zone or chamber of the pump, the transverse area of the entrance to the annular throat advantageously being greater than that of the nozzle exit but of smaller mean diameter.

Due to the inward tapering of the water jet, the thickness of the wall of water must neces- Further, while the inward tapering of the nozzle tends to cause a progressive decrease in the diameter of the water jet, this tendency is opposed by centrifugal force due to the whirling motion of the 'jet. These forces and opposing forces appear to build up in the unconfined water jet what I have designated internal or static pressure so that the water of the jet is under a pressure which is substantially higher than that of the low pressure chamber. Due to this higher pressure, the permissible temperature of the jet water is increased. Further, the water jet, produced as herein described, is surprisingly compact with a minimum of surrounding spray. I attribute this to the opposing forces just noted. This compact character of the stream and the increasing thickness of the wall of the annular jet also promote a more effective seal between the high and low pressure zones in the Venturi throatn The effectiveness of the jet is further 'increasedby the fact that the surface of the jet is increased due to its annular formation and the fact that both inner and outer surfaces of the jet are freely exposed to the atmosphere of the low pressure zone.

The jet pump of my present invention will usually be used in conjunction with conventional auxiliary exhausting apparatus, for instance, steam jet pumps, barometric legs, or the like, as fully understood by those familiar with this art.

The invention will be more particularly described and illustrated with reference to the accompanying drawings which represent conventionally, but not to scale, an especially advantageous embodiment thereof. It will be understood, of course, that the invention is not restricted to the particular structure shown. In these drawings Fig. 1 is a longitudinal sectional View of the ejector and housing;

Fig. 2 is a transverse section of the ejector along the line 22; and

Fig. 3 is a transverse sectional view, partly broken away, of the ejector and housing along the line 33.

The housing I delineates what is herein referred to as the low pressure chamber 2, which is in open communication at its upper end with the chamber to be evacuated. Below the low pressure chamber there is a high pressure chamber .3 delineated by the housing 4. The low pressure zone 2 is separated from .the high pressure zone 3 by an annular partition 5 which houses the annular chamber -6. Extending downwardly through a central opening in partition 5 and securely fastened thereto is a venturifl having a central core 8, coaxially positioned therein, each of circular transverse section, .so .as to form an annular Venturi throat 9. The central core is suspended in the venturi by any conventional means, for instance, by a spider .H), as shown in Figure 3.

The upper surface of the partition Sis provided with two oppositely positioned openings Ii. Extending upwardly from each .of said openings is a tubular conduit l2 which supports the annular chamber :3 and through which chamber 13 is in open communication with chamber 6.

The housing delineating chamber I3 projects downwardly and inwardly at its lower end to form the outer wall I 4 of an annular passageway or nozzle I5, the inner wall of said passageway being formed by the downwardly projecting elea to a central opening I? through which the high pressure chamber 3 is connected to a barometric leg indicated at IS. The high pressure zone 3 is connected at a point near its upper end to a steam jet pump or ejector diagrammatically represented at 19, the connection 20 being for the introduction of steam and the lower end of the steam ejector being equipped with a barometric leg 22.

In operation, water or other noncompressible fluid is forced under pressure through the pipe 2| into the annular chamber 6 and from thence passes upwardly through the oppositely positioned conduits i2 into the chamber IS, the conduits l2 being so positioned with respect to the chamber i3 that the water enters the chamber in a generally tangential direction so as to impart to the water a whirling motion. From chamber l3 the water passes as a whirling annular stream through the annular nozzle I 5. This annular nozzle I5 is so constructed and arranged 4 as to direct an unconfined annular stream of water toward the annular Venturi throat 9, the mean diameter of which is slightly less than the mean diameter of the exit of the annular nozzle The annular jet of water is exposed on all sides to the low pressure vapors within the low pressure chamber 2, so that all surfaces serve to induce the vapors through the venturi into the high pressure chamber. By reason of the whirling motion of the unconfined stream, there is a tendency toward an increase in diameter due to centrifugal force. However, this tendency is opposed by the tendency of the stream to decrease in diameter due to the inward direction imparted to it :by the annular nozzle.

As a result of these opposing forces, as previous'ly noted herein, the tendency of the stream to scatter or become disbursed as liquid droplets in the surrounding gaseous medium is materially reduced. Further, .as also previously noted, the unconfined stream appears .to be under an internal or static pressure which materially raises the temperature at which the liquid will vaporize at a given pressure.

The ejected vapors will be partially condensed in the enlarged section of the venturi due to in creased pressure, as well understood by the art. Such condensate, together with the jet water, is withdrawn from chamber 3 through the barometric leg l8 and uncondensed vapors and gases will be withdrawn from this high pressure chamber by means .of the steam jet is.

As indicated in the drawings, the various elements of the pump may be separately cast or forged and fastened together by means of flanges and casings in the conventional manner, as shown.

The specific embodiment of the invention shown in the drawings is particularly advantageous because of ease and economy of fabricating and assembling the various elements. It will be understood, however, that the construction or fabrication of the pump and these various elements is subject to considerable variation without departing from the scope of the invention.

For instance, instead of introducing the water through chamber 6, as .shown, that chamber may be dispensed with and the water introduced directly through other suitable connections tangentially into the annular chamber 13. Further, it will be understood that a plurality of nozzles and Venturi assemblies may be housed within a single pump chamber.

In the foregoing description, I have attempted to explain the unexpected effectiveness of my pump. It will be understood, however, that the utility of the invention is in no wise dependent upon the accuracy of such explanation.

Regardless of any theory, it is possible by use of the jet pump of my present invention, using jet water at a temperature for instance, of 76 F. to eject and condense vapors which, under prevailing pressure conditions, would otherwise condense only at 68 F., while iin using conventional jet pumps, it is necessary that the ejector water be at a temperature below that at which the vapors will condense. It will be understood that in place of the steam jet pump l8, one may use other types of pumps, for instance, a water ejector or a mechanical pump.

I claim:

1. A. jet pump comprising a housing enclosing a low pressure chamber and a high pressure chamber, a partition within said housing separating said chambers, an annular venturi extending through said partition, the transverse area thereof increasing in the direction of the higher pressure chamber, an annular nozzle tapering inwardly toward its exit end positioned coaxially with and spaced apart from, the annular venturi and directed toward the throat of the venturi, an annular water chamber coaxially positioned with respect to the nozzle and in open communication with the upstream end thereof, conduit means leading tangentially into said annular chamber, a passageway extending through said nozzle and water chamber, whereby the interior surface oi" the jet is exposed to the atmosphere of the low pressure chamber, an inlet to the low pressure chamber and an outlet from the high pressure chamber.

2. A jet pump comprising a housing enclosing a low pressure chamber and a high pressure chamber, a partition within said housing separating said chambers, an annular venturi extending through said partition, the transverse area thereof increasing in the direction of the high pressure chamber, an annular nozzle tapering inwardly toward its exit and positioned in said low pressure chamber coaxially with and spaced apart from an annular venturi and directed toward the throat of the venturi, an annular water chamber coaxially positioned with respect to the nozzle and in open communication with the upstream end thereof, conduit means leading tangentially into said annular chamber, a passageway extending through said nozzle and water chamber, whereby the interior surface of the jet is exposed to the atmosphere of the low pressure chamber, an inlet to the low pressure chamber and an outlet from the high pressure chamber.

3. A jet pump comprising a housing enclosing a low pressure chamber and a high pressure chamber, a partition within said housing separating said chambers, an annular venturi extending through said partition, the transverse area thereof increasing in the direction of the high pressure chamber, an annular nozzle tapering inwardly toward its exit end, positioned coaxially with, and spaced from, the annular venturi and directed toward the throat of the venturi, means for supplying water to the annular nozzle so constructed and arranged that the water enters the nozzle as a stream whirling coaxially with respect thereto, a passageway extending through said nozzle whereby the interior surface of the jet is exposed to the atmosphere of the low pressure chamber, an inlet to the low pressure chamber and an outlet from the high pressure chamber.

FREDERICK J. MACKENZIE.

Country Date France Nov. 19, 1932 Number 

